This invention relates to a surgical method, specifically to a balloon-assisted method of achieving a percutaneous posterior or posterolateral spinal fusion, or percutaneous surgical repair of bone fractures.
Of all animals having a backbone, human beings are the only creatures who remain upright for significant periods of time. From an evolutionary standpoint, this erect posture has conferred a number of strategic benefits, not the least of which is freeing the upper limbs for purposes other than locomotion. From an anthropologic standpoint, it is also evident that this unique evolutionary adaptation is a relatively recent change and as such has not benefitted from natural selection as much as have backbones held in the horizontal attitude. As a result, the stresses acting upon the human backbone (or “vertebral column”), are unique in many senses, and result in a variety of problems or disease states that are peculiar to the human species.
The human vertebral column is essentially a tower of bones held upright by fibrous bands called ligaments and contractile elements called muscles. There are seven bones in the neck or cervical region, twelve in the chest or thoracic region, and five in the low back or lumbar region. There are also five bones in the pelvis or sacral region which are normally fused together and form the back part of the pelvis. This column of bones is critical for protecting the delicate spinal cord and nerves, and for providing structural support for the entire body.
Between the vertebral bones themselves there exist soft tissue structures—discs—composed of fibrous tissue and cartilage. The discs are compressible and act as shock absorbers for sudden downward forces on the upright column. More importantly, the discs allow the bones to move independently of each other to permit functional mobility of the column of spinal vertebrae. Unfortunately, the repetitive forces acting on these intervertebral discs during repetitive day-to-day activities of bending, lifting and twisting cause them to break down or degenerate over time.
Presumably because of humans' upright posture, their intervertebral discs have a high propensity to degenerate. Overt trauma, or covert trauma occurring in the course of repetitive activities disproportionately affect more highly mobile areas of the spine. Disruption of a disc's internal architecture leads to bulging, herniation or protrusion of pieces of the disc and eventual disc space collapse. Resulting mechanical and even chemical irritation of surrounding neural elements (spinal cord and nerves) cause pain, attended by varying degrees of disability. In addition, loss of disc space height relaxes tension on the longitudinal spinal ligaments, thereby contributing to varying degrees of spinal instability such as spinal curvature or lithesis.
The time-honored method of addressing the issues of neural irritation and instability resulting from severe disc damage have largely focused on removal of the damaged disc and fusing the adjacent vertebral elements together. Removal of the disc relieves the mechanical and chemical irritation of neural elements, while osseous union (bone knitting) solves the problem of instability.
Present methods of fusing the spine from a posterior or posterolateral approach involve making a midline incision over the spinal elements to be fused. The muscles of the spine are then dissected away from the bony vertebral elements with sharp implements or electro cautery and the free muscle tissue is then retracted laterally with great force to expose the vertebral elements to be fused. The process utilized is very traumatic to the muscle tissues and frequently results in considerable blood loss. A long unsightly midline scar is the long-term consequence of such a spinal operation. Atrophy or scarring and fibrosis of the retracted muscle tissue frequently occurs.